How do you know?
Faith in scientific observation.
One of the things that was interesting about Piaget's observations of learning in children, was the almost universal attainment of basic kinetic physics by children right around the age of 9 months, as I remember. What he observed was that at that age, children will begin to track objects that disappear from view. If a ball travels behind a couch, the child will begin to anticipate the ball coming back into view at the appropriate place and time with it's eyes. An act of faith in Newton's laws, I contend.
Good of the Designer to find a way to pack all that good "pre-learned" stuff into our DNA.
Didn't I once get into a discussion about Chompsky on this issue -- whether such skills are inborn or have to be learned? Mighty tight coding, in any case.